OPERATING SYSTEMS EXAM REVIEW /
QUESTIONS WITH DETAILED VERIFIED
ANSWERS / ALREADY GRADED A;
GUARANTEED TO SUCCESS
Operating System - ANS-Layer of software that manages and abstracts a computer's resources for its
users and applications
Why do we use operating systems? - ANS-Allows you to communicate with the computer without
knowing the computers language
Roles of OS? - ANS-Glue - ties stuff together
Referee- protect one program from another
Allusionist - hides stuff and provides abstraction
Kernel - ANS-lowest level of software running on the system, with full access to all of the capabilities of
the hardware
software w/ privileges
Microkernel - ANS-Structures the operating system by removing all nonessential components from the
kernel and implementing them as system and user-level programs
Reasons to include certain functionality in the kernel - ANS-Cuts down extra steps needed for an
application to access the services it needs
Reasons to exclude certain functionality in the kernel - ANS-Makes it easier to modularize and debug
user-level services
Context Switch - ANS-the switch between two contexts, typically the user (application) context and the
kernel context. Can also be applied to thread switches
why are context switches an essential feature of a multitasking OS? - ANS-Enables multiple processes to
share a single CPU
, system call - ANS-a user's request to the kernel to perform a task
trap - ANS-the transition from user mode to kernel mode, usually due to a timer firing, an exception, or
a system call.
interrupt - ANS-an asynchronous signal to the processor that some external event has occurred that may
require its attention (error, mouse click, timer)
Routine that forces a context-switch from user to kernel
signal - ANS-a way to communicate with information to a process about the state of other processes,
the OS, and hardware
role of interrupts in a modern OS - ANS-a timer that occurs in the cpu. Makes sure that the computer
isn't running a never ending process and are necessary to max out the output of multicore processors.
What does a process look like to the OS? - ANS-A process needs permission from the operating system
kernel before accessing the memory of any other process, before reading or writing to the disk, before
changing hardware settings, and so forth.
difference from process and thread? - ANS-Process - concurrency and isolation
Threads - concurrency without isolation
faster? process or threads? - ANS-threads
uses a lot more memory? process or threads? - ANS-processes
takes more time to terminate? process or threads? - ANS-process
crashes and affects the rest? process or threads? - ANS-threads
crashes and doesn't affect the rest? process or threads? - ANS-process
take longer for context switches? process or threads? - ANS-process
share memory? process or threads? - ANS-threads
has own PCB, stack, and address space? process or threads? - ANS-process
have their parent's PCB, its own TCB and stack and common address space? process or threads? - ANS-
threads
Process Controls Blocks - ANS-Stores all the information the operating system needs about a particular
process
What is stored in a PCB? - ANS-where it is stored in memory, where its executable image resides on disk,
which user asked it to execute, what privileges the process has, and so forth.
QUESTIONS WITH DETAILED VERIFIED
ANSWERS / ALREADY GRADED A;
GUARANTEED TO SUCCESS
Operating System - ANS-Layer of software that manages and abstracts a computer's resources for its
users and applications
Why do we use operating systems? - ANS-Allows you to communicate with the computer without
knowing the computers language
Roles of OS? - ANS-Glue - ties stuff together
Referee- protect one program from another
Allusionist - hides stuff and provides abstraction
Kernel - ANS-lowest level of software running on the system, with full access to all of the capabilities of
the hardware
software w/ privileges
Microkernel - ANS-Structures the operating system by removing all nonessential components from the
kernel and implementing them as system and user-level programs
Reasons to include certain functionality in the kernel - ANS-Cuts down extra steps needed for an
application to access the services it needs
Reasons to exclude certain functionality in the kernel - ANS-Makes it easier to modularize and debug
user-level services
Context Switch - ANS-the switch between two contexts, typically the user (application) context and the
kernel context. Can also be applied to thread switches
why are context switches an essential feature of a multitasking OS? - ANS-Enables multiple processes to
share a single CPU
, system call - ANS-a user's request to the kernel to perform a task
trap - ANS-the transition from user mode to kernel mode, usually due to a timer firing, an exception, or
a system call.
interrupt - ANS-an asynchronous signal to the processor that some external event has occurred that may
require its attention (error, mouse click, timer)
Routine that forces a context-switch from user to kernel
signal - ANS-a way to communicate with information to a process about the state of other processes,
the OS, and hardware
role of interrupts in a modern OS - ANS-a timer that occurs in the cpu. Makes sure that the computer
isn't running a never ending process and are necessary to max out the output of multicore processors.
What does a process look like to the OS? - ANS-A process needs permission from the operating system
kernel before accessing the memory of any other process, before reading or writing to the disk, before
changing hardware settings, and so forth.
difference from process and thread? - ANS-Process - concurrency and isolation
Threads - concurrency without isolation
faster? process or threads? - ANS-threads
uses a lot more memory? process or threads? - ANS-processes
takes more time to terminate? process or threads? - ANS-process
crashes and affects the rest? process or threads? - ANS-threads
crashes and doesn't affect the rest? process or threads? - ANS-process
take longer for context switches? process or threads? - ANS-process
share memory? process or threads? - ANS-threads
has own PCB, stack, and address space? process or threads? - ANS-process
have their parent's PCB, its own TCB and stack and common address space? process or threads? - ANS-
threads
Process Controls Blocks - ANS-Stores all the information the operating system needs about a particular
process
What is stored in a PCB? - ANS-where it is stored in memory, where its executable image resides on disk,
which user asked it to execute, what privileges the process has, and so forth.
